[Qemu-devel] [PULL 0/2] virtio: fixes

[Qemu-devel] [PULL 0/2] virtio: fixes

[Michael S. Tsirkin]

The following changes since commit 6bbbb0ac136102098a70b97ab0c07bc7bf53131c:

  target-arm: Fix warn about implicit conversion (2016-08-12 11:12:24 +0100)

are available in the git repository at:

  git://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git tags/for_upstream

for you to fetch changes up to 58a83c61496eeb0d31571a07a51bc1947e3379ac:

  virtio: decrement vq->inuse in virtqueue_discard() (2016-08-23 19:20:24 +0300)

----------------------------------------------------------------
virtio: fixes

some bugfixes for virtio
balloon is still broken wrt migration

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

----------------------------------------------------------------
Stefan Hajnoczi (2):
      virtio: recalculate vq->inuse after migration
      virtio: decrement vq->inuse in virtqueue_discard()

 hw/virtio/virtio.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

[Qemu-devel] [PULL 1/2] virtio: recalculate vq->inuse after migration

[Michael S. Tsirkin]

From: Stefan Hajnoczi <stefanha@redhat.com>

The vq->inuse field is not migrated.  Many devices don't hold
VirtQueueElements across migration so it doesn't matter that vq->inuse
starts at 0 on the destination QEMU.

At least virtio-serial, virtio-blk, and virtio-balloon migrate while
holding VirtQueueElements.  For these devices we need to recalculate
vq->inuse upon load so the value is correct.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 15ee3a7..6105c6e 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1648,6 +1648,21 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
             }
             vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]);
             vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);
+
+            /*
+             * Some devices migrate VirtQueueElements that have been popped
+             * from the avail ring but not yet returned to the used ring.
+             */
+            vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
+                                vdev->vq[i].used_idx;
+            if (vdev->vq[i].inuse > vdev->vq[i].vring.num) {
+                error_report("VQ %d size 0x%x < last_avail_idx 0x%x - "
+                             "used_idx 0x%x",
+                             i, vdev->vq[i].vring.num,
+                             vdev->vq[i].last_avail_idx,
+                             vdev->vq[i].used_idx);
+                return -1;
+            }
         }
     }
 
-- 
MST

[Qemu-devel] [PULL 2/2] virtio: decrement vq->inuse in virtqueue_discard()

[Michael S. Tsirkin]

From: Stefan Hajnoczi <stefanha@redhat.com>

virtqueue_discard() moves vq->last_avail_idx back so the element can be
popped again.  It's necessary to decrement vq->inuse to avoid "leaking"
the element count.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 6105c6e..74c085c 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -268,6 +268,7 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
                        unsigned int len)
 {
     vq->last_avail_idx--;
+    vq->inuse--;
     virtqueue_unmap_sg(vq, elem, len);
 }
 
-- 
MST

Re: [Qemu-devel] [PULL 0/2] virtio: fixes

[Peter Maydell]

On 23 August 2016 at 17:34, Michael S. Tsirkin <mst@redhat.com> wrote:
> The following changes since commit 6bbbb0ac136102098a70b97ab0c07bc7bf53131c:
>
>   target-arm: Fix warn about implicit conversion (2016-08-12 11:12:24 +0100)
>
> are available in the git repository at:
>
>   git://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git tags/for_upstream
>
> for you to fetch changes up to 58a83c61496eeb0d31571a07a51bc1947e3379ac:
>
>   virtio: decrement vq->inuse in virtqueue_discard() (2016-08-23 19:20:24 +0300)
>
> ----------------------------------------------------------------
> virtio: fixes
>
> some bugfixes for virtio
> balloon is still broken wrt migration

Is this a bug we need to fix for the release?


> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> ----------------------------------------------------------------
> Stefan Hajnoczi (2):
>       virtio: recalculate vq->inuse after migration
>       virtio: decrement vq->inuse in virtqueue_discard()
>
>  hw/virtio/virtio.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)

Applied to master, thanks.

-- PMM